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Abstract:

The present invention relates to a paper for adhesive tapes having an
impregnated paper support containing recycled cellulose fibers as well as
to adhesive tapes comprising such a paper for adhesive tapes and an
adhesive layer. The recycled cellulose fibers are only slightly ground
and originate predominantly from the group of long-fibered softwood
celluloses. If necessary, the adhesive tape paper is provided with a
separating layer and a bonding agent layer.

Claims:

2. The paper for adhesive tapes according to claim 1, wherein the
recycled cellulose fibers are softwood cellulose fibers.

3. The paper for adhesive tapes according to claim 1, wherein the
recycled cellulose fibers originate from unsized waste paper grades of
group 4 according to the European List of CEPI/B.I.R.--standard grades.

4. The paper for adhesive tapes according to claim 1, wherein the
grinding degree of the recycled cellulose fibers is less than 50.degree.
Schopper Riegler.

5. The paper for adhesive tapes according to claim 1, wherein a
laboratory sheet, which consists of 100% recycled cellulose fibers, has a
weight per unit area of 70 g/m2 and is formed according to the
Rapid-Kothen method, has a breaking strength in dry condition of at least
35 N/15 mm and/or a suction height of more than 0 mm.

6. The paper for adhesive tapes according to claim 1, wherein the
splitting strength of the impregnated paper support is greater than 1.7
N/15 mm.

7. The paper for adhesive tapes according to claim 1, wherein one side of
the paper support is provided with a separating layer.

8. The paper for adhesive tapes according to claim 7, wherein the paper
support has a bonding agent layer on the opposite side of the separating
layer.

9. The paper for adhesive tapes according to claim 7, wherein said paper
is calendared.

10. The paper for adhesive tapes according to claim 9, wherein the paper
is calendared between a steel roller and a rubber roller at a splitting
pressure of 30 to 300 N/mm and a temperature between about 20.degree. C.
and 70.degree. C.,

11. The paper for adhesive tapes according to at claim 1, wherein the
amount of recycled cellulose fibers in the impregnated paper support is
>50%, preferably ≧90%, based on the total of cellulose fibers
contained therein.

12. An adhesive tape, comprising a paper for adhesive tapes according to
claim 1 and an adhesive layer.

13. A method of producing a paper for adhesive tapes according to claim
1, wherein the paper pulp containing recycled cellulose fibers and
optionally additives for paper production is ground and processed into a
paper support web which is subsequently impregnated.

14. The method of producing an adhesive tape, comprising the application
of an adhesive onto the paper for adhesive tapes according to claim 1.

15. (canceled)

16. The paper for adhesive tapes according to claim 1, wherein the amount
of recycled cellulose fibers in the impregnated paper support is greater
than 90%, based on the total of cellulose fibers contained therein.

17. The method of producing an adhesive tape, comprising the application
of an adhesive onto the bonding agent larger according to claim 8.

Description:

FIELD OF THE INVENTION

[0001] This invention relates to a paper for adhesive tapes (adhesive tape
paper) having an impregnated paper support containing recycled cellulose
fibers, to an adhesive tape containing such an adhesive tape paper as
well as to methods of producing the adhesive tape papers and adhesive
tapes.

BACKGROUND OF THE INVENTION

[0002] Adhesive tapes made of an extensible paper support which is
provided with a plastics impregnation and has an adhesive layer on one
side and an adhesive-repellent layer on the opposite side, have been
known for a long time. These adhesive tapes are wound on a core made of
board or plastics to give a roll. Here, the adhesive-repellent layer of
the adhesive tape paper, which is often referred to as a separating layer
or also as a "release coat", directly contacts the adhesive layer. The
adhesive-repellent impact of the separating layer is matched with the
adhesive force of the particular adhesive employed. As a result, the
individual layers of an adhesive tape roll strongly adhere to one another
such that they do not separate spontaneously, causing the adhesive tape
roll to fall apart. On the other hand, the adhesion of the adhesive to
the separating layer is not strong enough for the adhesive tape to tear
off when it is peeled off the roll. Such adhesive tapes are described in
DE 38 35 507 A1, for example.

[0003] These adhesive tapes are mainly used for masking objects during
painting and varnishing, in the production and processing of electronic
components and for sealing packages. Having been used, the adhesive tapes
are thrown away and end up in waste combustion or on the waste site. From
an environmental point of view, this is not an optimum step in particular
if for the production of the adhesive tapes primary raw materials, e.g.
primary celluloses, are used for the paper support.

[0004] In order to improve the environmental friendliness of adhesive
paper tapes, it was tried to supply them to waste paper recycling. On
account of their structure it is, however, not possible to recover the
cellulose fibers from most of the adhesive paper tapes during waste paper
processing. The adhesive paper tapes act like plastics films. They are
rejected in the waste paper process and also end up on the waste site or
are combusted.

[0005] Some efforts were made in the past to recover at least part of the
rather high-grade and valuable cellulose fibers.

[0006] For example, German patent specification DE 42 11 510 C2 describes
an adhesive packing tape which can be recycled and printed. In this case,
a sized kraft paper made of long-fiber sulfate cellulose is used as a
paper support, which was produced according to the Clupak method. It is
thus possible to dispense with an impregnation of the paper support.
Since the impregnation is dispensed with, at least part of the cellulose
fibers can be recovered during waste paper processing. However, a
drawback of this adhesive tape is that when the paper support is
dissolved in the waste paper process the adhesive layer is comminuted and
not completely removed from the pulp. In the further course of paper
production, these adhesive residues then interfere with the production as
they create holes and sticky deposits and cause the paper web to tear
off.

[0007] In addition, an impregnation of the paper support can only be
dispensed with for adhesive tapes which, after use, do not have to be
removed from the covered background without leaving any residue, as is
the case for adhesive packing tapes. Adhesive tapes for painting and
varnishing usually adhere very strongly to the background such that a
non-impregnated paper support splits if it is tried to tear off the
adhesive tape. Splitting or delamination means that the adhesive tape
paper tears off in itself, i.e. parallel to the adhesive tape, when it is
removed so that the adhesive layer and part of the adhesive tape paper
are left on the covered background. This is, of course, undesirable.

[0008] A conceivable alternative approach serving for obtaining more
environmentally friendly adhesive tapes might be to replace valuable,
high-grade primary raw materials with recycled raw materials, e.g. to
replace primary celluloses with recycled cellulose fibers in the case of
adhesive tape papers. As a result, it would no longer be necessary to
fell and process trees for this disposable article, i.e. the adhesive
paper tape.

[0009] DE 44 04 045 A1 makes an attempt in this direction. This
publication describes an adhesive tape for use as a lint roller where the
support tape is fully made of recycled waste paper. This document points
out that papers made of recycled waste paper have a small inner strength
and therefore are generally not suited for use as a support for adhesive
tapes. The invention according to DE 44 04 045 A1 is only possible
because a very weak adhesive is used at the same time. This adhesive
binds lints and dirt but only adheres very weakly to the rear side of the
paper support and to tables, for example. According to the teaching of DE
44 04 045 A1 the adhesive force of the bonding adhesive is said to be
generally smaller than the inner strength of the support tape (paper
support). This serves for avoiding the paper support to split and tear
off due to its small inner strength when a layer of the adhesive tape is
wound off the lint roller. DE 44 04 045 A1 does not discuss either the
type of recycled cellulose employed or the production process of the
adhesive tape paper. An adhesive tape according to this teaching is fully
unsuited for technical use. The adhesive is far too weak to reliably
adhere to most surfaces. if, however, the adhesive force of the adhesive
was increased, the adhesive would adhere excessively to the rear side of
the adhesive tape paper and the adhesive tape would tear because of its
very small inner strength in the attempt to wind off one or more layers.
Even if was possible to remove a layer of adhesive tape from the roll, it
would not be possible to easily remove it from the covered article again
since on account of its small inner strength it would split here as well.

[0010] JP 06-248244 A describes a release paper for adhesive tapes, which
may also consist of recycled waste paper among other products. This
publication does not specify the type of waste paper fiber employed and
the production process either. The release paper has a separating layer
made of a silicone compound to which even very strong adhesives adhere
only slightly and therefore can be removed again with very little effort.
The inner strength is usually irrelevant in this connection. However, in
contrast to adhesive tape papers, release papers are not coated with an
adhesive to then be adhered to an article. They rather serve as a
protective layer for the adhesive of an adhesive tape prior to use.
Before the adhesive tape is to be adhered to an article, the release
paper is pulled off the adhesive. Assuming that such a release paper per
se was coated with an adhesive, the inner strength of the described
release paper would again be too small to remove it completely from the
covered article without leaving any residue. The inner strength or
splitting resistance is the force which has to be overcome to split a
paper web into two individual layers.

[0011] Thus, there was a need for environmentally friendly adhesive tapes
which simultaneously have excellent mechanical properties to be usable
for masking articles in painting and varnishing, in the production and
processing of electronic components and as adhesive packing tapes, for
example.

SUMMARY OF THE INVENTION

[0012] The object of the present invention is to provide an adhesive paper
tape and an adhesive tape paper usable therein, which is more
environmentally friendly than conventional adhesive tapes as described in
DE 38 35 507 A1, for example, and which still has the required strength
and resilience to be suitable for use in masking articles in painting and
varnishing, in the production and processing of electronic components and
as adhesive packing tapes.

[0013] This object is achieved according to the invention by a paper for
adhesive tapes, which comprises an impregnated paper support and is
characterized in that the paper support contains recycled cellulose
fibers. Advantageous embodiments of the adhesive tape paper follow from
claims 2 to 11. An adhesive tape comprising such an adhesive tape paper
and an adhesive layer is the subject matter of claim 12.

[0014] The preamble of claim 1 here reflects the teaching of DE 38 35 507
A 1. Advantageous embodiments of the invention are described in the other
claims.

[0015] Surprisingly enough, the inventors have found that adhesive tape
papers including an impregnated paper support containing recycled
cellulose fibers have mechanical properties which are relevant for said
applications and are almost the same as those of an adhesive tape paper
made of high-grade primary cellulose. This could not be expected from an
expert point of view. The reason is that it had to be expected that due
to their short fiber lengths e.g. the recycled cellulose fibers
originating from waste paper would have strengths too small in order to
be usable in adhesive tape papers for the above described fields of
application.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary Embodiments

[0016] The adhesive tape according to the invention, which is in
particular an adhesive paper tape, comprises an impregnated paper support
that contains recycled cellulose fibers and is provided with an adhesive
layer on at least one side thereof. In order to better fix the adhesive
layer, the adhesive tape paper may additionally be coated with a bonding
agent before the adhesive is applied. If the applied adhesive is a
pressure sensitive adhesive and only one side of the adhesive tape paper
is provided with an adhesive layer, it is advantageous to provide the
other side of the adhesive tape paper with an adhesive-repellent
separating layer. In order to increase softness and smoothness, the
impregnated adhesive tape paper can be calendared before the adhesive is
coated.

[0017] The present application uses the term "recycled" cellulose fibers
synonymously with "recovered" cellulose fibers. These cellulose fibers
are recovered from waste paper, for example. The amount of recycled
cellulose fibers in the impregnated paper support is preferably >50%,
more preferably ≧90% and even more preferably ≧95%, based
on the total cellulose fibers contained therein (i.e. recycled cellulose
fibers+non-recycled, i.e. primary, cellulose fibers). According to a
particularly preferred embodiment, the impregnated paper support
exclusively contains recycled cellulose fibers and no primary cellulose
fibers, i.e. non-recycled cellulose fibers, in the adhesive tape paper
according to the invention.

[0018] Recycled cellulose fibers particularly suited according to the
invention have proven to be those recovered from unsized group 4 waste
paper grades (kraft grades) according to the "European list of standard
grades of recovered papers (CEPI/B.I.R.) and their qualities", July 2000.
Preferred waste paper grades are tissue papers, tissue kraft papers and
sulfate boards. These waste paper grades are characterized by high
strengths and a low grinding degree or freeness of the cellulose fibers
contained therein. They contain a particularly great amount of softwood
cellulose fibers (e.g. spruce, pine tree, etc.). Softwood cellulose
fibers generally have a markedly greater fiber length than cellulose
fibers made from broadleaf trees. Correspondingly, it is advantageous as
regards the strength of the adhesive tape paper according to the
invention for the recycled cellulose fibers to be long-fiber softwood
cellulose fibers.

[0019] The recycled cellulose fibers employed according to the invention
advantageously have the properties listed in the below table. In order to
measure these properties, a laboratory sheet having a weight per unit
area of 70 g/m2 and consisting of 100% recycled cellulose fibers to
be investigated was produced according to the Rapid-Kothen method.

[0020] The production method according to Rapid-Kothen is to be described
in more detail below. The cellulose to be investigated was dried at
105° C. in a circulation air drying cabinet for 4 hours. 24 g of
the thus dried cellulose was increased to a cellulose-water volume of
2000 ml by the addition of tap water for the purpose of disintegration,
followed by corresponding comminution. The suspension is then supplied to
the disintegration container. The disintegration is carried out at a
propeller rotating speed of 3000 rpm for precisely 25 minutes at a
container content temperature of 15 to 20° C. At the time of
sampling serving for forming the laboratory sheet, the distribution state
of the cellulose fibers in the cellulose suspension has to be quite
uniform. This is achieved by good mixing using suitable mixing vessels.
For example, the pulp suspension may be transferred to a distributor.
Then, the mixture is diluted using tap water to a cellulose-water volume
of 9000 ml. Thereafter, the distributor is started and the suspension is
mixed until it is filled into the 1 liter measuring cylinders for at
least 2 minutes and no more than 10 minutes.

[0021] A Rapid-Kothen sheet formation and drying system is used for the
actual formation of the laboratory sheet and drying thereof. This system
is equipped with a couch roller (diameter (102-130 mm), length (240-260
mm), weight (3±0.2 kg); lateral surface made of felt having a
thickness of 20 mm), for example.

[0022] Having an aspired weight per unit area of 70 g/m2, about 800
ml of the resulting pulp suspension are filled into the 1 l measuring
cylinders. The filling chamber of the Rapid-Kothen sheet formation and
drying system is flooded with water. Air is pressed into the filling
chamber which contains about 4-5 l of water and the pulp suspension is
poured in. Swirling is allowed for 5 seconds, the air supply is stopped
and the water is sucked off as quickly as possible. Thereafter, air is
sucked through the sheet for 10 seconds. A paper cover sheet is placed
centrically onto the wet sheet. The couch roller is allowed to roll back
and forth into two mutually orthogonal directions without additional
pressure over the sheet in 2 seconds. The sheet formation screen is
removed from the support screen, turned over and its edge is smacked in
slightly inclined fashion onto a horizontal base such that the wet sheet
and the cover sheet fall down. 1 minute after couching at the latest, the
wet sheet resting on the cover sheet is placed on the support screen of
the drier. Another cover sheet is placed on top of the wet sheet, the
drier is then closed immediately and evacuated by means of a vacuum pump.
The drying step is carried out for 8-10 minutes at about 96° C.
and with a partial vacuum of 95 kPa.

[0023] In this application, a test sheet produced in this way from the
cellulose fibers whose properties are to be investigated is referred to
as a laboratory sheet formed according to the Rapid-Kothen method.

[0024] The standard relevant for the Rapid-Kothen method is DIN EN ISO
5269-2.

[0025] The recycled cellulose fibers which are used according to the
invention in a particularly beneficial fashion have the properties listed
in the below table (laboratory sheet formation according to Rapid-Kothen;
laboratory sheet weight 70 g/m2):

[0026] The paper support is made from the paper pulp containing recycled
cellulose fibers according to the prior art as known, possibly existing
dirt particles in the paper pulp being removed by conventional graders.
In the paper pulp, the amount of recycled cellulose fibers is as
mentioned above, i.e. preferably >50%, more preferably ≧90% and
even more preferably ≧95%, based on the total of cellulose fibers
contained therein. It is particularly preferred for the paper pulp to
consist of unsized group 4 waste paper grades (kraft containing grades)
according to the "European list of standard grades of recovered paper
(CEPI/B.I.R.) and their qualities", July 2000. The paper pulp is ground
with the grinding units common for the production of adhesive tape paper,
preferably with a maximum energy input that is only 40 to 80%, more
preferably 50 to 70% of the energy input required for grinding primary,
long-fiber softwood sulfate celluloses. The grinding is advantageous to
increase the strength of the paper support. It is additionally possible
to provide the paper pulp, if required, with the additives common in
paper production, such as wet strength agents, retention agents, fillers
and/or dyes.

[0027] The paper web of the paper support may additionally be given a
higher stretch or extension. This may be done, for example, by wet
creping, dry creping or the Clupak method but is not limited to these
examples. Every process providing the paper web with an additional
stretch is suitable for the production of the paper support.

[0028] In the wet creping method, the moist web adhering to the surface of
a cylinder is already removed in the paper machine by means of a scraper
abutting the cylinder. A difference between the driving speed of the
creping cylinder and that of the following transfer and drying unit,
which may be adjusted to 2 to 50%, causes the paper web to be "creped" by
this amount, i.e. to be made shorter by this amount due to the production
of fine crimps.

[0029] The dry creping method operates according to a similar principle
except that the creping is made outside the paper machine. The already
dried paper is moistened before it is fed to the creping apparatus.

[0030] In the Clupak method, the still moist paper web is compacted
between a rotary roller and a rotating elastic web, usually a rubber
blanket. As a result, the extensibility of the paper is obtained with a
very smooth surface.

[0031] The thus produced paper support has a weight per unit area of 30 to
100 g/m2. preferably 35 to 60 g/m2, an elongation at break of 2
to 20%, preferably 5 to 15%, a breaking strength in dry condition and
longitudinal direction of 25 to 100N/15 mm, preferably 25 to 60 N/15 mm,
a breaking strength in dry condition and transverse direction of 20 to 80
N/15 mm, preferably 10 to 20 N/15 mm, a splitting strength of at least
1.7 N/15 mm, preferably of at least 2.5 N/15 mm, and a thickness of 0.05
to 0.150 mm, preferably 0.100 to 0.120 mm.

[0032] The paper support is subsequently impregnated. This means that the
paper support is soaked with an impregnating agent. A distinction has to
be made between an impregnation and an only superficial coating. The
impregnation is necessary to provide the adhesive tape paper according to
the invention and an adhesive tape made thereof with the necessary
strength and flexibility and create a non-absorbent base for the
subsequent coatings. Suitable impregnating agents are polymer
dispersions, polymer solutions or mixtures thereof.

[0035] An impregnating agent particularly suited according to the
invention is an aqueous styrene-butadiene-rubber dispersion having a
glass transition temperature between -30° C. and +10° C.,
preferably between -10 and +5° C. The impregnating agent amount is
between 5% by weight and 50% by weight, preferably between 10% by weight
and 20% by weight, of the dry dispersion, based on the weight of the
paper support to be impregnated.

[0036] Various additives and/or fillers may be added to the impregnating
agent. Examples of additives are dyes, crosslinkers, hydrophobing agents,
oil-repellent agents, hydrophilizing agents or mixtures thereof. For
example, kaolin, titanium dioxide, talcum, calcium carbonate, silicon
dioxide or mixtures thereof may be used as fillers.

[0037] In a special embodiment of the adhesive tape paper, a separating
layer is applied to one side of the impregnated paper support. This
separating layer may be produced by applying an aqueous dispersion based
on acrylic acid esters, polyvinyl acetate, acrylic acid-styrene
copolymers, styrene butadiene rubber, long-chain fatty acid and/or fatty
alcohol derivatives, paraffins, silicone compounds or mixtures thereof,
for example. As a result of the mixing ratio of the components used in
this connection, the effect of the separating layer can be matched with a
large number of different adhesives. The application amount after drying
(dry coating amount) is 1-5 g/m2, preferably 2-3 g/m2.

[0038] Another variant of the adhesive tape paper according to the
invention results from the application of a bonding agent on the side of
the impregnated paper support which is not provided with the separating
layer, i.e. on the side which is coated with the adhesive in the
production of the adhesive tape, so as to form a bonding agent layer. The
bonding agent preferably consists of an aqueous dispersion based on
natural latex, acrylonitrile butadiene rubber, styrene butadiene rubber,
acrylic acid ester or mixtures thereof. The application amount after
drying (dry coating amount) is 1-5 g/m2, preferably 1-2 g/m2.

[0039] Both the impregnating agent and the separating layer as well as the
bonding agent may be admixed with various additives and/or fillers.
Examples of additives are dyes, crosslinkers, hydrophobing agents,
oil-repellent agents, hydrophilizing agents or mixtures thereof. For
example, kaolin, titanium dioxide, talcum, calcium carbonate, silicon
dioxide or mixtures thereof may be used as fillers.

[0040] The impregnation of the paper support and the coating of the
impregnated paper support may be made either inside the paper machine or
outside the latter in an impregnation and coating machine designed for
this particular purpose. Suitable impregnating methods are e.g. size
press, dip impregnation, foam impregnation, roll impregnation, or
spraying. Suitable coating methods are e.g. roll doctor, doctor blade,
air brush or roller application.

[0041] In order to increase surface smoothness and flexibility, it is
possible to calendar the impregnated paper coated with the separating
layer and/or bonding agent. It is here preferred for the adhesive tape
paper according to the invention to pass through the gap of a pair of
rollers consisting of a steel roller and a rubber roller at a splitting
pressure of 30 to 300 N/mm, preferably 50 to 150 N/15 mm, the side with
the separating layer contacting the steel roller. The calendar
temperature is between 20° and 70° C., preferably between
60 and 70° C.

[0042] In order to produce the adhesive tape, the adhesive tape paper
according to the invention is also provided with an adhesive layer. If
the adhesive tape paper, has a separating layer, the adhesive is applied
to the opposite side. The employed adhesive may be either a pressure
sensitive adhesive or an adhesive activated by moistening using a
solvent, preferably water, or by heat. In consideration are all types of
adhesive known for adhesive paper tapes in the art. The selection of a
suitable adhesive depends on the intended use of the adhesive tape
according to the invention. The application weight of the adhesive ranges
between 20 g/m2 and 50 g/m2, preferably between 30 g/m2
and 35 g/m2.

Test Methods

[0043] Weight per unit area according to DIN EN ISO 536

[0044] Thickness according to DIN EN ISO 534 having a support pressure of
20 N and a measuring surface of 200 mm2

[0045] Breaking strength in dry condition and in longitudinal and
transverse directions according to DIN EN ISO 1924-2

[0046] Elongation at break in dry condition and in longitudinal and
transverse directions according to DIN EN ISO 1924-2

[0052] Suction height in longitudinal and transverse directions according
to DIN ISO 8787

[0053] Tear resistance according to Elmendorf in accordance with DIN EN
21974 with a sample package of 4 paper sheets

[0054] Freeness according to Schopper Riegler DIN ISO 5267-1

Splitting Strength:

[0055] A strip having a width of about 52 mm and a length of about 200 mm
is cut out of an adhesive tape paper sample conditioned beforehand at
23° C. and 50% relative humidity for 24 hours. The side having a
length of 200 mm here extends parallel to the running direction of the
paper. A strip of the adhesive test tape Scotch 2836 having a width of 50
mm and a length of about 150 mm is then adhered to this sample. The
adhesive test tape is adhered to the side of the adhesive tape paper
sample to be examined that has the strongest adhesion with respect to the
adhesive test tape. Then, the composite of the adhesive tape paper to be
examined and the adhesive test tape are joined by pressing using a steel
roller having a weight of 4.5 kg and a width of 50 mm. The steel roller
is rolled manually twice over the composite without exerting an
additional pressure (once back and once forth). Thereafter, 2 strips
having a width of 15 mm and the entire length are cut out of this
composite. The adhesive test tape is pulled off manually from one of the
two sides where the adhesive tape paper to be examined protrudes such
that the adhesive tape paper to be examined is split over the entire
sample width. If the adhesion of the adhesive test tape on the adhesive
tape paper to be examined is poor and if the splitting strength is very
high, the adhesive tape paper to be examined must be carefully cut by a
razor blade and then be further split by means of the adhesive test tape.
The splitting strength is measured in a Roll type Z 0.5 universal testing
machine of Zwick company, having the following settings:

[0056] The manually removed Scotch 2836 adhesive test tape is clamped into
the upper clamp of the tensile testing machine. The adhesive tape paper
to be tested is clamped in the lower clamp of the universal testing
machine such that the composite protrudes at an angle of 90°
relative to the tensile direction. During the measurement, care must be
taken that the splitting is made in the center of the adhesive tape paper
to be tested and that not only individual fibers are pulled out of the
paper surface. Measurements where the splitting is not made in the center
are ignored and repeated. What is measured is the average force required
to split the paper. The result is the mean value from two individual
measurements.

Example 1 (Exemplary Embodiment)

[0057] In order to produce the adhesive tape base paper, 100% waste paper
of the tissue kraft paper grade, brown, available from C.A. Lensing
Entsorgung GmbH was used under the designation of tissue kraft paper,
brown/white. The cellulose fibers of this waste paper grade had the
following properties (measured by means of a laboratory sheet, produced
according to the Rapid-Kothen method in accordance with DIN EN ISO
5269-2; weight of the laboratory sheet 70 g/m2):

[0058] A paper web was made as usual from the above described waste paper
in a paper machine. The energy input during grinding was 10 kWh/100 kg
fiber mass. The paper web was transferred in a still moist state on a
creping cylinder from where it was removed by a scraper as described in
DE 4019680 A1 and subsequently dried by means of a drying cylinder. The
thus produced adhesive tape base paper (paper support) had the following
properties:

[0059] The paper support of the adhesive tape paper was then soaked in a
dip impregnation with an aqueous styrene butadiene rubber dispersion of
the Litex SX 1009 grade, available from Polymerlatex company, and
subsequently dried. The rubber has a glass transition temperature of
-6° C. The impregnation weight was 5 g/m2 after drying, which
corresponds to a percentage of 10.2%, based on the fiber amount.

[0060] In another process step, the impregnated paper was coated on one
side with 3 g/m2 of a separating layer consisting of Primal R253 of
Rohm and Haas company and on the opposite side with 1 g/m2 of a
bonding agent consisting of Graftex 49 of Centrotrade company. The paper
was fully dried after each coating step.

[0061] Finally, the impregnated and coated adhesive tape paper was
calendared between a steel roller and a rubber roller at a splitting
pressure of 50 N/mm and a temperature of 70° C. In this case, the
side of the separating layer contacted the steel roller.

[0062] The properties of the thus produced impregnated and coated adhesive
tape paper are listed in Table 1.

Example 2 (Comparative Example)

[0063] In order to produce the adhesive tape base paper, NBSK grade
cellulose, available from Canfor company under the designation of
Interconti ECF 90, was used. The cellulose fibers of this cellulose grade
had the following properties (measured by means of a laboratory sheet
produced according to the Rapid-Kothen method in accordance with DIN EN
ISO 5269-2; weight of the laboratory sheet 70 g/m2):

[0064] A paper web was made as usual from the above described cellulose in
a paper machine. The energy input during grinding was 17 kWh/100 kg fiber
mass. The paper web was transferred in a still moist state to a creping
cylinder from where it was removed by a scraper as described in DE
4019680 A1 and then dried by means of a drying cylinder. The thus
produced adhesive tape base paper had the following properties:

[0065] A wet creped paper web was made from the thus produced cellulose
pulp according to a prior art method. It had the following properties:

[0066] The thus produced paper web was then impregnated by means of dip
impregnation with an aqueous styrene butadiene rubber dispersion of the
Litex 1009 grade, available from Polymerlatex company. The rubber had a
glass transition temperature of -4° C. The impregnation weight was
15 g/m2 after drying, which corresponds to a percentage of 40% by
weight, based on the fiber amount.

[0067] In another process step, the impregnated paper was coated on one
side with 3 g/m2 of a separating layer consisting of Primal R253 of
Rohm and Haas company and on the opposite side with 1 g/m2 of a
bonding agent consisting of Graftex 49 of Centrotrade company. The paper
was fully dried after each coating step.

[0068] The properties of the thus produced adhesive tape paper are listed
in Table 1.

[0069] The comparison of the two examples makes clear that in spite of the
use of recycled cellulose fibers the adhesive tape paper according to the
invention (Example 1) has almost the same properties as an adhesive tape
paper made of high-grade primary cellulose (Example 2) and is thus suited
for all conventional intended uses. The differences in the elongation at
break in dry condition and longitudinal direction follow from the machine
settings in the creping step and are not due to the different fiber
application. As expected, the splitting strength of the paper according
to the invention (Example 1) is lower than that of a paper having
high-grade primary celluloses (Example 2). Surprisingly enough it is,
however, high enough to comply with the requirements occurring during
further processing and use.